This invention relates generally to bimetallic plates used as actuators for electronic and other devices and more particularly to the modification and improvement of such bimetallic actuators to primarily prevent the bimetallic actuators from losing calibration by preventing the transfer of forces and stresses to the calibrated areas of the bimetallic actuator during manufacture and assembly of the various types of electronic and other devices in which such bimetallic actuators are used and also more particularly to the use of such improved bimetallic actuators to enable greater miniaturization to be achieved for various types of electronic components such as cycling, non-cycling or manually resettable circuit breakers using such improved bimetallic actuators.
The use of bimetallic actuators in electronic components such as circuit breakers is generally disclosed in the prior art. This is shown in U.S. Pat. Nos. 2,503,008; 2,828,385; 3,141,080; 3,143,614; 4,379,278 and 4,803,455.
Those skilled in the art know that in bimetallic actuators such as snap-acting or cantilevered types of such actuators, the response time for the critical operating condition to be met must be accurate for the given electronic component. Therefore, such bimetallic actuators are calibrated, within the tolerance standards, for the application in which the given electronic component will be used so the response time for the condition being monitored by the electronic component will at all times remain accurate.
One of the problems which affects the accuracy of the calibration for a given bimetallic actuator is that which occurs during manufacture and assembly of the bimetallic actuator into the associated electronic component or other device. The calibration characteristics of the bimetallic actuator can be materially altered due to force stresses transferred into the calibrated areas of the bimetallic actuator caused by the particular manufacturing procedures such as welding, riveting, crimping or spring loading, used when either affixing contacts onto or when affixing the bimetallic actuator into assembled position on the associated electronic component or other device.
If the calibration characteristics of the bimetallic actuator are materially altered, the accuracy, function and operation of the electronic component or other device in which the bimetallic actuator is used will be compromised and the device will be rendered unusable and unsalable for the particular rating for such electronic component or other device. Of even greater significance in the commercial marketplace is the fact that this problem becomes increasingly complex as the size, thickness and other required characteristics of the bimetallic actuator are reduced to obtain or manufacture smaller or miniaturized versions of existing electronic components or other devices or to create new designs of such electronic components or other devices which utilize such bimetallic actuators as the, or one of the, critical operating elements. The improved bimetallic actuator in accordance with the present invention provides means to overcome this problem and provides other benefits in the manufacture and operation of the electronic components or other devices in which they are used.
Thus, in one aspect of the present invention, a bimetallic actuator is prevented from losing or being thrown out of calibration during attachment of contacts onto the bimetallic actuator and/or during affixation of the bimetallic actuator into assembled position during the manufacture and assembly of electronic components, electrical systems and other devices using such bimetallic actuators, by drawing, stamping or molding a contoured area or areas such as a generally raised or recessed annular shape on a given bimetallic actuator about either or both the point where an operative contact is to be located on the bimetallic actuator or the point where the bimetallic actuator is to be affixed into assembled position on the electronic component or other device. The raised or recessed annular shaped area or areas are preferably formed so that at all points the annular area or areas lie inwardly of the edges of the bimetallic actuator. These contoured area or areas are shaped to increase the rigidity of these area or areas on the bimetallic actuator so that they become inert and thus prevent the transfer of forces or stresses caused by welding, riveting, crimping or spring loading during manufacturing and assembly of the electronic component or other device using such bimetallic actuator.
While reference is made to the contoured area or areas as raised or recessed annular shapes, it is not necessary that such raised or recessed annular shapes be circumferentially integral. Thus, the annular shape may encompass a plurality of closely spaced arcuate sections or circumferentially disposed indentations without departing from the scope of the present invention. Further, however, it will be equally clear to those skilled in the art that generally integral annular raised or recessed annular shapes are preferred as they are the most effective means for achieving the advantageous results of the present invention such as the reduction in size and the miniaturizing of electronic components using such bimetallic actuators.
It is also known that the prior art electronic components with bimetallic actuators such as circuit breakers generally are too large for many applications. This compels the user with such applications to sacrifice the desirable protection afforded by such circuit breakers.
This occurs in the electronic components and other devices using bimetallic actuators because the problems which alter the calibration of the bimetallic actuator become even more significant and complex, when efforts are made to reduce the size of or to miniaturize the electronic components or other devices, because corresponding changes must be made to the bimetallic actuator in size, thickness and the materials from which the bimetallic actuator is made to achieve the desired calibration for the given component or device. These changes to the bimetallic actuator place the calibrated areas of the bimetallic actuator closer to the areas where the stress forces arise during manufacture and assembly, and because of their proximity these forces can now travel more easily into the calibrated areas so that calibration is either lost or thrown off, rendering the associate electronic component or device unusable and unsalable in the commercial marketplace for the required conditions of operation.
Thus, in addition to the advantageous features that the modified and improved bimetallic actuator in accordance with the present invention may have for use in larger electronic components, electrical systems and other devices, in another aspect of the present invention, it has been found that the modified or improved bimetallic actuator is particularly suitable for use in and to provide miniature circuit breakers substantially smaller than the prior art devices, thereby making such components more practical and desirable for use in motor vehicles and other devices which require protection of the electrical components in their electrical systems or the electrical system itself where mandatory, preferred or desired size limitations are specified by the users of such protective devices.
Thus, it is another aspect of the present invention to provide improved miniature bimetallic actuated circuit breakers of the cycling, non-cycling and manually resettable types utilizing bimetallic actuators having means defining contoured areas, one of said contoured areas formed about the point of connection for permanently affixing the bimetallic actuator into assembled position on one of the current carrying members in the bimetallic actuated circuit breaker and optionally and selectively at least another of said contoured areas a spaced distance therefrom for connecting a contact member to the bimetallic actuator, said contact member generally disposed in assembled position for coaction with the other current conducting member in the circuit breaker during operation thereof.
The contoured areas may be defined by a raised or recessed annular shape or shapes formed by stamping or molding on the bimetallic actuator and act to prevent the transfer of forces to the calibrated portions of the bimetallic actuator which occur during the manufacture and assembly of the miniature bimetallic actuated circuit breakers, thereby preventing the bimetallic actuator from being thrown out of calibration. The raised or recessed annular area or areas achieve this result because they increase the rigidity at these locations on the given bimetallic actuator. In addition, these raised or recess annular area or areas provide piloting for various assembly operations, insure more uniform and favorable welding results, simplify and decrease the cost of manufacturing the circuit breaker and provide means for achieving greater miniaturization of the circuit breakers in which such bimetallic actuators are used.
Thus, the present invention pertains generally to a bimetallic actuator for use in electronic components and other devices having, at least one contoured area about any selected location that will transmit stress forces into the calibrated areas of the bimetallic actuator during manufacture or assembly of the bimetallic actuator in associated electronic components.
The present invention also pertains to a miniature bimetallic actuated circuit breaker for protecting components in a current carrying circuit from damage which comprises, a sized and shaped housing, a first current carrying member, a second current carrying member in spaced relation to said first current carrying member, a bimetallic actuator having, a connecting location for fixedly connecting the bimetallic actuator to said first current carrying member, and a location or point for connecting a contact means spaced from said connecting location, contact means to be connected to said bimetallic actuator and in connected position for operative engagement with said second current carrying member, a contoured area about at least one of said location for the connecting means and the point of connection for the contact means, said contoured area to prevent the transfer of stress forces into the calibrated areas of the bimetallic actuator whereby said bimetallic actuator will operate at the predetermined calibration and prevent damage to the miniature bimetallic circuit breaker and the current carrying circuit in which it is mounted.
Accordingly, it is an object of the present invention to provide an improved bimetallic actuator for use in electronic components and other devices in which the transfer of stress forces is prevented to insure that the calibration of the bimetallic actuator remains substantially constant.
It is another object of the present invention to provide an improved bimetallic actuator used in forming miniature circuit breakers of the cycling, non-cycling or manually resettable type for applications in which it is desirable to use a smaller circuit breaker than are presently commercially available.
It is another object of the present invention to provide an improved miniature circuit breaker which can be manufactured at a relatively low cost.
It is still another object of the present invention to provide an improved bimetallic actuator for use in an improved miniature circuit breaker where a generally contoured area or areas are formed about either or both of the points for connecting the bimetallic actuator in assembled position and the contact means on said bimetallic actuator to provide heat dissipation sinks and increase the rigidity in such area or areas so as to prevent distortion of said bimetallic actuator during welding, riveting, crimping or spring loading which would otherwise cause the actuator to be thrown out of calibration, thereby enabling electrical devices such as circuit breakers to be miniaturized to meet modern day miniaturization demands.
It is a still further object of the present invention to provide an improved bimetallic actuator for use in an improved miniature circuit breaker where a generally contoured area or areas such as raised or recessed annular area or areas are drawn, struck or molded about either or both of the points for the connection of the bimetallic actuators into assembled position for use or for the formation of the operative contact means on said bimetallic actuator, to increase rigidity of the actuator in such areas, and thereby protect the performance characteristics of electronic devices using such bimetallic actuators such as circuit breakers.
It is a further object of the present invention to provide an improved bimetallic actuator including at least one generally contoured area or areas having either a raised or recessed annular shape that serves as a pilot location means for consistently welding said bimetallic actuator onto a current carrying member.
It is a further object of the present invention to provide for generally contoured areas having either raised or recessed annular shapes on a bimetallic actuator for use in an improved miniature circuit breaker to create more favorable weld results and simplicity in manufacturing.
It is another object of the present invention to provide a bimetallic actuator with generally contoured annular members either raised or recessed about either or both the point of connection and the contact means on the bimetallic actuator to allow for non-invasive connection thereof to avoid changing the calibration of the bimetallic actuator during assembly, provide more efficient operation and allow for decreasing the physical size of a circuit breaker or other electronic component.
These and other objects of the present invention will be more clearly understood from the description when read in conjunction with the accompanying drawings.